Nikoli Handmade Puzzles - as good as all that?

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Nikoli Handmade Puzzles - as good as all that?

Postby PaulIQ164 » Wed Oct 19, 2005 4:14 pm

Here's what Nikoli say on their website about handmade versus computer-made puzzles:

Let's consider a puzzle that has been made using a computer program. If you are a reasonably experienced solver, you might wish to tackle it. You will soon discover that making a start is difficult. There are no cells in which to place a number using straightforward techniques. I'll show you what to do. Look at box one (upper-left 3x3). There is no 6 in this box, but there are 6s in columns one and three. So, in box one, a 6 can only go in column two, but there are two possible cells. Next, let's look at 1. In box four (centre-left 3x3) and box seven (bottom-left 3x3) there are no 1s. But there are 1s in rows four, six, seven and nine. In box four, a 1 can only go in row five, and in box seven a 1 can only go in row eight. This means that columns one and three cannot be used for a 1 in box one. The two cells of column two in box one will be occupied by a 1 and a 6. Using this information, you can find the cell that contains an 8 in box one. That's right - column one, row two. Now, all of the 8s can be placed easily. Once you have discovered how to solve this problem, the puzzle presents no other difficulties.
Can you really say that you enjoy solving this kind of puzzle? I never can. Computer-generated Sudoku puzzles are lacking a vital ingredient that makes puzzles enjoyable - the sense of communication between solver and author. The best Sudoku make you concentrate, but aren't stressful. They are absorbing, never boring.


That was said regarding this puzzle:
Image

Anyway, here's puzzle 70 from issue 7 of Sudoku Magazine, containing Nikoli puzzles:

Code: Select all
9  ¦  6¦ 7
 3 ¦1  ¦  5
  5¦   ¦3 
---+---+---
 5 ¦4 2¦  3
   ¦   ¦   
7  ¦8 9¦ 5
---+---+---
  4¦   ¦8 
6  ¦  7¦ 9
 1 ¦2  ¦  6


As far as I can tell, to solve this puzzle you need to find a hidden pair in box 2 (which is easiest to find by first finding another hidden pair in that box), find another pair, in row 4 (again, easiest if you found the first pair), use the second pair to find another pair inbox 8, and from that pair and the first pair, place a number in box 8. After all that, everything in the puzzle is trivial. This is exactly what they accuse CG puzzles of being like (though they never are, in my experience). So do the handmade puzzles have anything to offer?
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Postby lunababy_moonchild » Wed Oct 19, 2005 8:19 pm

Well, I've been enjoying the hand-made (by Nikoli) puzzles that I've been doing. Their Super-Difficult rated, in the book that I'm using - Carol Vorderman's Massive Book of Sudoku - is rated Medium by Pappocom software and I find them suitably challenging. That may be because I'm rubbish at solving though! I can and have done a Pappocom Fiendish in 35 minutes and I can say that this feels different to the hand-made ones by Nikoli.

I can also say that a puzzle I got involved with in the Daily Mail's supplement of a few weeks ago also felt totally different to the Nikoli ones.

Do the hand-created ones have any more to offer than CG? I don't know, I don't think that I'm at a high enough solving level to say - I solve on paper without any of the advance techniques (as far as I'm aware!).

Luna
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Postby GLmathgrant » Thu Apr 27, 2006 2:55 am

There's actually a rather easier way to get started.

As you pointed out, there is a "naked pair" in box 2. Well, that naked pair can be used to locate a hidden pair in box 8. Once you have that hidden pair, there will be a digit that can go in only one of the cells in row 9. The rest of the puzzle can then be solved with singles.

I myself had done computer-generated puzzles for a long time, but then I tried one of Nikoli's "Hard"-rated puzzles, and found it to be considerably more fun and relaxing than all the computer-generated puzzles I'd ever tried. Of course, considering that this is the official forum for a Sudoku-generating program, I think it's safe to say that I'm in the minority here.:)
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